1. Field of the Invention
The present invention relates to a process for producing 4-benzoyl-5-hydroxypyrazoles or salts thereof (hereinafter referring to as 4-benzoylpyrazole derivatives) which are useful as active ingredients or intermediates or herbicides. More particularly, it relates to a process for producing 4-benzoylpyrazole derivatives by a condensation reaction of a pyrazolone derivative and a benzotrichloride derivative followed by a hydrolysis reaction.
2. Description of the Prior Arts
Heretofore, it has been known to produce 4-benzoylpyrazole derivatives by a reaction of a pyrazolone derivative with a benzoyl halide derivative in U.S. Pat. No. 4,063,925; and U.S. Pat. No. 4,008,200. In the processes, a 5-benzoyloxypryrazole derivative is produced as an intermediate and then, benzoyl group at 5-position of the intermediate is rearranged at 4-position to obtain 4-benzoylpyrazole derivative. Thus, the benzoyl halide derivatives used as the starting materials in the process have tearing properties that are the starting materials in the process have tearing properties that are easily effectively used. Moreover, the benzoyl halide derivative has been produced by a chlorination reaction of a side chain of toluene or a halogenotoluene followed by a hydrolysis reaction of the resulting product. The benzoyl halide derivative has been also produced by oxidizing toluene or halogenotoluene and reacting the resulting benzoic acid derivative with phosphorus trichloride, phosgen or thionyl chloride. The process comprises many steps and is expensive.